1. Field of the Invention
This invention relates to a tape position detection apparatus and, more particularly, to a tape position detection apparatus for detecting the position of a tape or a film wound on reels in a video or audio tape recorder.
2. Description of the related art
The conventional video tape recorder uses a tape position detector to confirm the running position of the loaded tape. In order for the tape position to be detected by such an apparatus, the tape is first run for a predetermined period of time. Data relating to the speed or frequency of rotation of at least the reels, on which the tape is wound, is obtained by the detector, and is substituted in a predetermined equation for calculation. Thus, in the case of the above video tape recorder, the tape position cannot be calculated unless reproduction, a fast feed, or a rewind operation is first carried out immediately after the cassette tape has been loaded therein.
The rotation of the reels, however, is considerably unstable in case when the reels are not rotated by more than one rotation due to the excentricity of the reels and the state, in which the tape is wound on the reels. In order to determine the tape position with accuracy, therefore, it is necessary to wait at least until the reels complete one rotation. This means that in case of a reproduction mode, particularly of a tape where data is recorded in a long time mode, a considerable time is required until the display of the tape position is obtained.
Actual tape position display in a VHS format video tape recorder requires time as follows. With a cassette tape loaded in the video tape recorder, a time from the instant of start of tape loading caused by depressing a reproduction key till the instant when the tape position display is obtained, is measured. The measured time is approximately 15 seconds with a tape where data is recorded in a standard mode and approximately 30 seconds with a tape where data is recorded in a long time mode.
When the forward/reverse high speed reproduction mode, which is also known as the fast forward/reverse reproduction mode is employed in order to determine the tape position, the tape position can be displayed sooner than in the case where the normal reproduction mode is used. This is because in the fast forward/reverse reproduction mode, the tape is fed about five times faster than in the case of the normal reproduction mode. However, the tape is fed up to a position, which is considerably spaced apart from the position before the start of fast forward/reverse reproduction, and it has to be returned, manually, to the initial position, which is a time-consuming operation.
As has been shown, detecting the tape position by means of the prior art tape position detection apparatus is a relatively lengthy process and requires returning the tape to its original position prior to the commencement of the position detection operation. Moreover, it cannot be guaranteed that the tape will be returned to its exact pre-detection position. As a result, it has, until now, not been possible to satisfy the demand of being able to confirm the tape position or residual tape amount immediately, after the loading of the cassette tape into a recorder.